These font files can be created from existing TrueType font files using Microsoft's Web Embedding Fonts Tool (WEFT), and other proprietary and open source software (see “External links” below).

The font files are made small in size by use of subsetting (only including the needed characters), and by data compression (LZ compression, part of Agfa's MicroType Express). Like OTF fonts, EOT supports both Postscript and TrueType outlines for the glyphs.[1]

Simply including fonts in webpages might lead to unrestricted copying of copyrighted font files. Embedded OpenType includes features to discourage copying. Subsetting reduces the value of copying, as subsetted fonts will typically omit more than half of the characters. Other copy protection measures used are encryption and a list of "trusted roots" at the source end, and a proprietary decrypting library at the receiving end.

If the embedded font is not available to the web page for any reason (missing font file, wrong keys in the file, non-support by the web browser), then the second-choice font specification is used, ensuring that the page should be readable even without the intended font.

WEFT scans the HTML document file(s), the TrueType font file(s), and some additional parameters. It adjusts the HTML files and creates Embedded OpenType files for inclusion on the web site. These files usually use the extension ".eot".

WEFT can embed most fonts, but it will not embed fonts that have been designated as 'no embedding' fonts by their designers. WEFT may reject other fonts because problems have been identified.

Embedded fonts are widely used to generate non-English-language websites.

As of January 2015, the most recent version of the tool (WEFT 5.3.2) was released on 25 February 2003.

Microsoft PowerPoint 2007 and 2010 also generate .eot files with the ".fntdata" [2] extension when fonts are selected to be embedded in a presentation by the PowerPoint client application. These .eot files can be extracted from the ".pptx" file and used directly on web pages.